A conventional objective lens driving means provided in the optical pickup of an optical disc drive is composed of a moving part on which an objective lens is mounted, supporting members for supporting the moving part, focusing coils, tracking coils, a yoke, and magnets.
When a drive current is applied to the focusing coils, electromagnetic force is produced by the interaction of the current with the magnetic flux developed by the magnets. The electromagnetic force drives the moving part in the focusing direction, which is either toward or away from the optical disc surface. Similarly, when a drive current is applied to the tracking coils, electromagnetic force is produced by the interaction of the current with the magnetic flux from the magnets. The electromagnetic force drives the moving part in the tracking direction, which is the direction radially with respect to the optical disc.
However, in cases in which inclination of the objective lens is caused when the moving part is moved in the focusing or tracking direction, optical aberration is generated, resulting in a possible adverse effect in recording/reading information on the optical disc. Thus, an objective lens driving means having small inclination when the moving part is moved is demanded.
Patent Document 1 discloses an example of a conventional structure of such objective lens driving means in the optical pickup. The publication discloses an example of such structure comprising a first yoke and a second yoke to which magnets are attached, so that the position of the second yoke with respect to that of the first yoke can be adjusted in the tracking direction. The publication discloses that the inclination of the moving part caused when the center of a magnetic circuit and that of the moving part are shifted due to dimension errors or fabrication errors in parts can be suppressed. See JP Patent Publication (Kokai) No. 2001-184683 A (page 5, FIG. 2)